1. Field of the Invention
The present invention relates to a mask for transferring an illuminated pattern to a transfer area, and an exposure method and an exposure apparatus for transferring the pattern on the mask to a transfer area on a substrate. More specifically, the present invention relates to an exposure method and an exposure apparatus, and a mask suitable for pattern joining exposure at a transfer area on a substrate.
2. Description of the Related Art
In general, as an exposure apparatus for producing a liquid crystal display element or the like, there is one involving a so-called step and repeat method (stepper) in which after exposure of a pattern formed on a mask onto a predetermined exposure area on a photosensitive substrate, the photosensitive substrate is stepped by a certain distance, and exposure of the pattern of the mask is repeated.
Conventionally, when for example an LCD pattern for a liquid crystal display element having a large area is formed by the stepper, a screen synthesis method has been normally used.
With this screen synthesis method an LCD pattern in which a plurality of patterns are synthesized, is formed on a glass substrate using a plurality of masks corresponding to respective divided LCD patterns, by a method where after a pattern on a mask has been exposed onto an exposure area of the glass substrate corresponding to one mask, the glass substrate is stepped and the mask is changed to another mask, and a pattern on the mask is exposed onto an exposure area corresponding to that mask.
FIG. 38 is a pattern diagram in which a circuit pattern 1 of a glass substrate (substrate) P used at the time of production of a 15-inch liquid crystal display device is severally divided (into 6 in the figure).
The circuit pattern 1 has an approximate square shape, and comprises a display section 2 and a peripheral section 3. The display section 2 comprises a pattern in which a plurality of electrodes corresponding to a plurality of pixels are disposed regularly. The peripheral section 3 is formed so as to surround the display section 2, and has a conductive section for connecting a pattern of each electrode in the display section 2 to a driver circuit (not shown) for driving the respective electrodes. The circuit pattern 1 is constructed such that the circuit pattern is synthesized by divided patterns A to F including the display section 2 and the peripheral section 3.
On the other hand, FIG. 39 is a plan view of masks RA to RF on which patterns corresponding to these divided patterns A to F are formed. With a stepper using these masks RA to RF, for example, the mask RA is first attached, and a glass substrate P is shifted to a predetermined position corresponding to the divided pattern A and then exposed, to thereby transfer the divided pattern A onto the glass substrate P.
Then, the mask RA is changed to the mask RB, and the glass substrate P is shifted to a predetermined position corresponding to the divided pattern B and then exposed, to thereby transfer the divided pattern B onto the glass substrate P. The divided patterns A to F are transferred to the glass substrate P by repeating his operation sequentially.
Moreover, FIG. 40 is a pattern diagram wherein a circuit pattern 4 of a glass substrate (substrate) P used at the time of production of a 21-inch liquid crystal display device is severally divided (into 15 in this figure). As described above, the circuit pattern 4 has such a construction as to be synthesized by divided patterns A to F2 including the display section 2 and the peripheral section 3. In this example, since a part of the display section 2 has a pattern where the divided patterns A, B and C are repeated, a plurality of shots are exposed with the same mask (for example, a mask having an A pattern). FIG. 41 shows masks RA to RF in which patterns corresponding to these divided patterns A to F2 are formed. Also in this case, as described above, by changing the masks sequentially, and shifting the glass substrate P to a predetermined position to thereby effect the exposure, the circuit pattern 4 is screen-synthesized.
When the above described screen synthesis method is performed, a difference in level occurs at a joint portion of the pattern due to a pattern rendering error of the mask, aberration of the lens of the projection optical system, positioning error of a stage where the glass substrate is to be stepped or the like, thereby impairing the properties of the device. Moreover, when the screen-synthesized divided patterns are overlapped in multiple layers, overlap error of the exposure area of each layer, and line width difference of the pattern change discontinuously at the joint portion of the patterns. Hence, to prevent the quality of the device from being degraded, a so-called pattern joining exposure is carried out.
This pattern joining exposure is to join and expose the joint portions in adjacent exposure areas, and in each exposure area, to proportionally reduce the exposure quantity (exposure energy quantity) in this joint portion toward the boundary by changing, for example, the exposure time, to thereby approximately match the exposure quantity in this portion with the exposure quantity in other portions, when the exposure is effected by overlapping the exposure areas. The pattern joining exposure is disclosed for example in Japanese Patent Application, First Publication Nos. Hei 6-244077 and Hei 7-235466.
However, the conventional exposure methods and exposure apparatuses and masks described above have the following problems.
Of the patterns formed on the respective masks RA to RF, the pattern in the display section 2 is such that a plurality of electrodes corresponding to pixels are regularly disposed. Therefore, even if the pattern is severally divided, a common alignment pattern partially exists in the respective divided patterns A to F.
With the divided patterns A to F however, the existence of the peripheral section 3 or the position to be connected by the peripheral section 3 is different, depending upon the position of the divided display section 2. Therefore, even if there is a partially common pattern, masks RA to RF corresponding to the divided patterns A to F must be prepared, which imposes a big burden on the cost. Moreover, if the number of masks increases, the time required for changing the masks also increases, causing a problem in that improvement of throughput is hindered.
In view of the above situation, it is an object of the present invention to provide a mask, and an exposure method and an exposure apparatus using this mask, wherein when exposure processing accompanying screen synthesis is performed for producing a device, cost can be reduced and throughput improved by exposing only a small number of masks.
To achieve the above described object, the present invention adopts the following construction.
The exposure method of the present invention is an exposure method for joining and exposing a first pattern and a second pattern on a substrate using a mask having a pattern, wherein the pattern on the mask has a common pattern for the first pattern and the second pattern, and a non-common pattern different from the common pattern and formed continuously with the common pattern, and the common pattern and at least a part of the non-common pattern are selected to effect the joining and exposing.
Therefore, with the exposure method of the present invention, when the second pattern is subjected to the pattern joining exposure after the first pattern is exposed on the substrate, the common pattern common to the first pattern and at least a part of the non-common pattern different from the common pattern can be selected for use. Hence, at the time of exposure of the second pattern, there is no need to separately prepare a mask having the second pattern.
Moreover, with this exposure method, a pattern on the mask can be multiply transferred to a plurality of exposure areas with one mask so that the patterns become different. Hence the time required for changing the masks can be reduced, and the throughput can be improved. In addition to this effect, since the number of masks to be used, which are very expensive, can be also reduced, there is also the resultant effect of realizing a cost reduction. This effect becomes particularly significant when the same pattern is repeatedly transferred, as with a liquid crystal display device or a semiconductor memory.
The exposure method in an other embodiment of the present invention is constructed such that the non-common pattern is formed on either side of the common pattern. With this exposure method, the time required for selecting the first pattern and the second pattern can be reduced. Hence the effect is obtained in that further improvement of the throughput can be realized.
The exposure method in an other embodiment of the present invention is constructed such that selection of the non-common pattern is different for when the first pattern is exposed to when the second pattern is exposed. With this exposure method, the first and second patterns having different patterns can be transferred with one mask. Hence the effect can be obtained that in addition to obtaining the effect that the time required for changing the masks can be reduced and the throughput can be improved, the cost can also be reduced due to the reduction in the number of expensive masks to be used.
The exposure method in an other embodiment of the present invention is constructed such that selection of masks is set by an illumination area of the mask, and an exposure area on the substrate corresponding to the illumination area is overlapped on an adjacent exposure area. With this exposure method, by setting the illumination area, the effect can be obtained that a pattern can be multiply transferred to a plurality of exposure areas with one mask so that patterns become different.
Moreover, when the exposure areas on the substrate corresponding to the illumination areas are arranged in a rectangular shape so that two sides thereof are overlapped respectively, a light attenuation area where the transmittance gradually changes is formed on one side of the illumination area, and the illumination areas corresponding to each exposure area can be shifted respectively along the abovementioned one side (in the X direction) during exposure. In this way, the exposure area on the substrate corresponding to the light attenuation area is exposed with the gradually changing exposure energy quantity. In the exposure area adjacent to this exposure area, the exposure energy quantity in the overlap portion can be made the same as that for other portions, by overlapping in the light attenuation area.
Hence, according to this exposure method, overexposure is not caused even in an area where the exposure areas intersect, and an effect can be obtained that the exposure can be effected with the same exposure quantity as with other exposure areas. Moreover, in this case, since the movement of the illumination area setting device is in one direction, an effect can be obtained that a drive mechanism for driving the illumination area setting device can be made simple.
Furthermore, when the exposure areas are arranged in a rectangular shape as described above, pairs are formed by the exposure area sets whose sides are overlapped, and in each pair, the illumination areas corresponding to the exposure area can be respectively shifted along the same direction (in the diagonal direction) during the exposure. Hence, in the intersection portion of the exposure areas disposed in the rectangular shape, exposure can be effected with half the energy quantity of others. Moreover also in the remaining pairs, by shifting the illumination areas in the same direction during the exposure, the intersection portion can be exposed with half the energy quantity of the other areas, and the combined exposure quantity becomes the same as the exposure quantity of the other areas. Hence, with this exposure method, overexposure is not caused even in an area where the exposure areas intersect, and an effect can be obtained that the exposure can be effected with the same exposure quantity as with other exposure areas.
The exposure method in an other embodiment of the present invention is constructed such that the same direction to which the illumination areas are shifted is the diagonal direction in the rectangular arrangement. With this exposure method, even when two orthogonal sides are overlapped and exposed at a time with the adjacent exposure area, overexposure is not caused even in an area where the exposure areas intersect. Hence an effect can be obtained that the exposure can be effected with the same exposure quantity as with other exposure areas.
The mask of the present invention is characterized in that corresponding to a plurality of patterns, a common pattern for the plurality of patterns and a non-common pattern different from the common pattern are continuously formed.
Therefore, with the mask of the present invention, by combining the common pattern and the non-common pattern different from the common pattern, one mask can correspond to a plurality of patterns. Hence, an effect can be obtained that the number of masks to be used can be reduced, thus realizing a cost reduction.
The mask in an other embodiment of the present invention is constructed such that the non-common pattern is formed on either side of the common pattern. With this mask, when a pattern including a common pattern is set, an effect can be obtained that the time required for the setting can be reduced.
The exposure apparatus of the present invention is an exposure apparatus comprising; a mask stage for holding a mask having a pattern, and an illumination optical system for illuminating the mask, for exposing the mask pattern on a substrate, wherein the mask is held on the mask stage, and the exposure apparatus comprises an illumination area setting device for setting the illumination area of the mask to at least a first illumination area and a second illumination area, and a control unit for joining a first pattern exposed on the substrate by means of the first illumination area and a second pattern exposed on the substrate by means of the second illumination area.
Therefore, with the exposure apparatus of the present invention, the illumination area of the mask held on the mask stage is set in the first illumination area using the illumination area setting device, so that the first pattern having at least a common pattern can be exposed on the substrate. Then, by setting the illumination area of the mask in the second illumination area using the illumination area setting device, a second pattern having at least a common pattern can be exposed on the substrate. At this time, the first and second patterns exposed on the substrate are joined by control of the control unit.
Hence with this exposure apparatus, by setting the illumination area by the illumination area setting device, a plurality of patterns can be set with one mask. Hence the effect can be obtained that in addition to obtaining the effect that the time required for changing the masks can be reduced and the throughput can be improved, the cost can be also reduced due to the reduction in the number of expensive masks to be used.
The exposure apparatus in an other embodiment of the present invention is constructed such that the illumination area setting device sets the illumination area of the mask in the first and second illumination areas in accordance with the position of a transmission portion formed by a plurality of sides, and the control unit joins the first and second patterns in the first and second illumination areas on the substrate, and the illumination area setting device incorporates a plurality of side constituents and a shift apparatus for shifting the side constituents respectively and independently.
With this exposure apparatus, the effect can be obtained that, illumination areas having different sizes and positions can be variously set according to the situation, exposure and shading of the light attenuation portion can be easily done, and pattern joining exposure having wide generality can be achieved.
The exposure apparatus in an other embodiment of the present invention is constructed such that a light attenuation portion where the transmission gradually decreases is provided on at least one side of the transmission portion. With this exposure apparatus, by shifting the illumination area along one side where the light attenuation portion is disposed during the exposure, overexposure is not caused even in an area where the exposure areas intersect. Hence an effect can be obtained that the exposure can be effected with the same exposure quantity as with other exposure areas. Moreover, in this case, the movement of the illumination area setting device is in one direction. Hence an effect can also be obtained that a drive mechanism for driving the illumination area setting device can be made simple.
The exposure apparatus in an other embodiment of the present invention is constructed such that there is provided a shift apparatus for respectively shifting the illumination areas corresponding to the exposure areas whose sides overlap to form a pair, along the same direction, when the exposure areas are arranged as a plurality of rectangles so that respective two sides thereof are overlapped. With this exposure apparatus, overexposure is not caused even in an area where the exposure areas intersect. Hence an effect can be obtained that the exposure can be effected with the same exposure quantity as with other exposure areas.
The exposure apparatus in an other embodiment of the present invention is constructed such that the same direction to which the illumination areas are shifted is the diagonal direction of the rectangular arrangement. With this exposure apparatus, when two orthogonal sides are overlapped and exposed at a time with the adjacent exposure area, overexposure is not caused even in an area where the exposure areas intersect. Hence an effect can be obtained that the exposure can be effected with the same exposure quantity as with other exposure areas.
The exposure apparatus in an other embodiment of the present invention is constructed such that the control unit drives the substrate stage in accordance with the setting of the illumination area setting device. With this exposure apparatus, the substrate stage drives in accordance with the setting of the illumination area setting device, to thereby transfer a plurality of patterns onto the substrate, with one mask. Hence the effect can be obtained that in addition to obtaining the effect that the time required for changing the masks can be reduced and the throughput can be improved, the cost can be also reduced due to the reduction in the number of expensive masks to be used.